When you say you can jump on it straight up and it's fine, but when
you plant leaned away it hurts, leads me to believe that you are not
planting your foot correctly. When you plant your foot to take off
from the curved approach, your foot should be aligned with your
direction of travel. Your direction of travel should be a line from
your takeoff point to the center of the bar.

What many jumpers do improperly is to point the foot toward the inside
of the curve from that path, so the toes are pointed parallel or even
away from the bar. This causes a lot of ankle problems.

If you are planting your foot correctly alligned with your direction
of travel at plant, the forces on your ankle are nearly the same as
they would be if you were just jumping from a straight run and jumping
straight ahead.

You may be trying to get your back toward the bar during the takeoff
drive - before you leave the ground. This would prompt you to point
your toes toward the inside of the curve. There are other
possibilities as well.

Your approach is probably at fault here. An approach that does not
deliver you to your takeoff point, leaned away from the the correct
amount, and headed in the right direction can cause a host of
problems. Let me know if you want to talk further about your approach.